Another kind of threat for island biodiversity

27 April 2012 | News story

Invasive alien species (IAS) are a global concern as they threaten biodiversity, health, food security, tourism and trade. Island ecosystems are most vulnerable to the impacts of IAS. Scientists say that 50%-67% of extinctions of terrestrial species on islands have been caused by the impacts of IAS.

"The threat is more severe on islands as many are biodiversity hotspots," says Ms Shyama Pagad, Manager, Information Services, IUCN SSC Invasive Species Specialist Group speaking at the Pacific Islands Species Forum in Honiara, Solomon Islands. “Many native species of Pacific Island countries and Territories are endangered and many more will suffer the impacts of invasive species if governments do not react accordingly".

Two severe examples of the devastating impacts of invasive species in the Pacific region are the introduction of the brown tree snake (Boiga irregularis) to Guam and the introduction of the predatory rosy wolf snail (Euglandina rosea) to French Polynesia. The predatory rosy wolf-snail has caused the extinction of 57 of 61 species of endemic Partulids (snails) in French Polynesia. On Guam, predation by the brown tree snake has devastated native birds and lizard species, driving several to extinction and has caused the disappearance of two of the three bat species. The tree-loving snake also coils around power lines and is responsible for hundreds of power outages on the island, causing significant cost and inconvenience to the islanders.

And IAS do not only appear on land, some sea weeds can be invasive for example, Kappaphycus and Eucheuma which weaken coral reefs, displace native species and have proven to be a nuisance on beaches.

While some species are introduced accidentally, others are introduced intentionally. "The fire ant (Wasmannia auropunctata) was introduced to Malaita in the Solomon Islands as a biological control for a Nut fall bug," says John Fasi of the Solomon Islands College of Higher Education. “It has become a pest, as it is known to inflict eye problems in domestic animals and give a painful bite to people, increasingly being encountered while gardening and near villages”. The Solomon Islands has 19 introduced species of ants alone including the invasive fire ant.

Eradication is being used as an effective management option to rid invasive species such as rats, cats, mongoose, dogs, goats and deer on islands. However, this process takes time and requires thorough studies of ecological relationships, issues of impacts on non-target species etc.

"It is important that governments invest in biosecurity to control what goes through their ports of entry," says Ms Souad Boudjelas, Program Manager of the Pacific Invasives Initiative. "We must really prevent these invasive species from spreading from country to country and island to island because their impacts are not only devastating to biodiversity but also to sectors like agriculture, trade, tourism and the economy as well".

The Guidelines for Invasive Species Management in the Pacific state that prevention and monitoring should be the first options for government. For long term control, public engagement, political leadership, research and information sharing underpin all management efforts.